Boil salted water in a large pot
Cook elbow macaroni until al dente
Drain the pasta and set aside
Melt butter in a saucepan over medium heat
Whisk in flour and cook for 1 to 2 minutes
Slowly whisk in milk until smooth
Cook, stirring, until the sauce thickens
Stir in shredded cheddar cheese until melted
Add salt, black pepper, and optional mustard powder or paprika
Mix the cooked macaroni into the cheese sauce
Stir until the pasta is evenly coated
Serve immediately